The drilling or production of oil and gas requires strings of pipe to be positioned in a borehole. The strings of pipe may extend both horizontally and vertically and they may be thousands of feet in length. A coil tubing string is sometimes inserted through the length of these pipe strings for use in clearing or cleaning the interior of these pipe strings. A “pig” may be placed at the end of the coil tubing prior to its insertion into the pipe string to assist in such clearing and cleaning. The pig may be placed on the end of jointed pipe or snubbing unit, or on strings of polymer or composite pipe to achieve the same result.
The pig used in conjunction with the coil tubing string is typically provided with a plurality of resilient cups or rings around its perimeter. These cups contact the interior wall surface of the pipe string when the pig is moved through the pipe string by the tubing string. These resilient cups are often made of rubber, polyurethane or other type of polymer material. Because the resilient cups are subjected to high temperatures, high pressures and abrasion as the pig is moved through the pipe string, these cups often wear, breakdown or become deformed.